This component is referred to as the common gamma chain (γc). The most common form of SCID, affecting nearly 30% of all cases, is due to a mutation in a gene on the X chromosome that encodes a component (or chain) called IL2RG shared by the T cell growth factor receptor and other growth factor receptors. Deficiency of the Common Gamma Chain of the T Cell Receptor While these patients can be diagnosed in infancy, particularly if SCID newborn screening is available, many are diagnosed later in life. In these patients, there are low numbers of T cells with reduced but not absent function. Recently, leaky or atypical (hypomorphic) SCID was described. Although they vary with respect to the genetic type that causes the immunodeficiency, some of their laboratory findings and their pattern of inheritance, these infants all have an absence of T cells and severe deficiencies in both T cell and B cell function. There are currently at least thirteen different genes that, when mutated (changed), cause SCID. These defects lead to extreme susceptibility to serious infections. SCID is a rare and fatal syndrome of diverse genetic causes in which there is combined absence of T lymphocyte and B lymphocyte function and in many cases also natural killer (NK) lymphocyte function. Fortunately, effective treatments, such as hematopoietic stem cell transplantation (bone marrow transplant), exist that can treat the disorder, and the future holds the promise of gene therapy for some types. This condition is generally considered to be one of the most serious forms of PI. These defects lead to extreme susceptibility to very serious infections.
There are at least 13 different genetic defects that can cause SCID. SCID is fatal without a stem cell transplant or corrective gene therapy.
Severe Combined Immunodeficiency (SCID, pronounced “skid”) is a serious primary immunodeficiency disease (PI) in which there is combined absence of T lymphocyte and B lymphocyte function.
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